THIS Manhattan rent tale could make Bill and Hillary’s office escapades look small by comparison.

As the United Federation of Teachers struggles to win a raise for city teachers, union chief Randi Weingarten was engaged in a separate set of top-secret negotiations – about rent.

We’re talking $11.48 million in rent. A year.

Multiply that by a 30-year lease, and you get $321.44 million – and that’s with two years of free rent thrown in by the landlord.

These talks were so hush-hush, members of the UFT’s executive board have been kept out of the loop.

I use the past tense because, after reluctantly spilling the details of the massive move all day, Weingarten last night suddenly told me she was scrapping the deal.

“Politically, it seemed like the wrong thing to do,” a furious-sounding Weingarten said.

We’ll see.

But there’s no changing the fact that even as she seeks re-election as UFT president, Weingarten has been deep into negotiations about moving her union’s headquarters from lower Park Avenue to more-spacious digs in the downtown Financial District.

She is eyeing the tower atop 25 Broadway – a 23-story, neo-Renaissance building that was built in 1921 as headquarters for the Cunard cruise-ship line.

The building’s tower portion, which measures 280,000 square feet, once contained a penthouse for the use of Cunard honchos, according to a spokeswoman for the rental agent, Newmark & Co. Real Estate Inc. Until recently, it was occupied by Standard & Poor’s.

Weingarten said the building’s owner offered to lease the space for about $41 a square foot, with the first two years rent-free.

Take out your calculators: The tab comes out to $11.48 million a year.

The union leader said the UFT had hoped to get an option to buy the building, which leases space to, among others, the office of Special Schools Investigator Ed Stancik.

Weingarten said the $41-a-foot rental was below the area’s market rate of $50 to $60 a square foot. However, a downtown real-estate expert told me that figure sounded high for the building.

To help pay the rent, Weingarten told me the UFT was looking to sell some of the three office buildings it owns on Park Avenue South, which recently has transformed into a hot neighborhood and could fetch a stellar price.

Weingarten said that the Broadway office space would require renovation. But she said the UFT’s existing offices are so aged and cramped, the downtown deal could wind up saving money.

“The phone lines are on the fritz, we have to redo the windows” on the Park Avenue offices, she said.

Weingarten acknowledged that she started a top-secret office hunt six months ago. Negotiations on the 25 Broadway space were moving along, she claimed, when two weeks ago she decided to “slow things down” due to concerns about terms of the lease.

As Randi’s Rent Story becomes public here today, it certainly has the potential to work up controversy among UFT members, who currently are engaged in union elections.

“They want to keep this deal quiet until after Randi is re-elected,” one union source charged, speaking on condition of anonymity.

The pricey rent deal may offend some members, because the union is at a standstill in its quest to win teacher raises from Mayor Giuliani.

Among other things, the mayor wants to base teacher pay on individual performance; the union has insisted on across-the-board pay raises.

Retired and current teachers have until April 4 to return their union election ballots. When votes are counted on the 5th, Weingarten is expected to win big against Fort Hamilton HS English teacher Michael Shulman.

Yesterday, Shulman expressed surprise at the secrecy of his rival’s lease negotiations.

“The information has not come to the executive board,” said Shulman, who counts six supporters on the 89-member panel. “That’s pretty extraordinary.”

Shulman would not comment on the proposed lease, because he said he’s not familiar with the details.

Details, of course, were hard to come by because the UFT doesn’t want to share information with the members who pay union honchos’ salaries and headquarters’ rent.

The last time Weingarten was caught engaging in this kind of secrecy, she and schools Chancellor Harold Levy were cooking up an unusual perk for summer-school teachers: They wanted to give each teacher one round-trip airplane ticket as a form of raise.

The proposal was withdrawn after I publicized it in this column.

If a new headquarters makes financial sense for the union, Weingarten should share the information with the members who rely on her judgment.